Police departments from several cities combined to arrest at least 280 motorists on suspicion of driving under the influence of drugs or alcohol during an annual summer “Avoid the 25” operation, according to the Contra Costa Sheriff’s Office.

The 18-day crackdown began Aug. 20 and concluded Sept. 6. The arrest totals are expected to increase because statistics are still being compiled, the Sheriff’s Office said.

During the campaign police agencies conducted several operations including a multiagency effort that targeted drivers on Interstate 680. They also engaged in roving DUI saturation patrols, a warrant and probation sweep of repeat offenders and those with DUI warrants, sting operations targeting drivers with suspended licenses who drove to court hearings, and several DUI and driver’s license checkpoints.

In addition to evacuating 10 neighboring homes, deputies restricted pedestrian and vehicle traffic in the area while the sheriff's office bomb squad "safely disposed" of the explosives, officials said.